Realtime Worlds was founded in 2002.

A single user OS could also be a real-time system. The differences in the two are based on how a process is given control or priority within the system. Realtime systems give preferences to realtime control processes (realtime runs at a much higher priority level).

Most single-user operating systems treat processes with equal priority unless you indicate that a certain process is to receive preferential treatment. This can be done by raising the priority of the user process to that of realtime, meaning it will receive resources (such as CPU cycles) above other programs in the system.

Realtime Interrupt was created in 1995.

Realtime Associates was created in 1986.

Realtime Worlds ended in 2010.